Field of Invention
The invention relates to a bearing for a pump with a shaft rotating around an axial direction in accordance with the preamble of the independent device claim as well as to a pump. The invention further relates to a method of retrofitting a bearing for a pump.
Background Information
For the bearing of the rotating shaft of a pump there are many solutions known in the art. In particular in horizontally arranged pumps it is a known technology to use oil rings, also referred to as slinger rings to supply the bearing with a lubricant. The oil ring hangs loosely on the shaft or on a part that is connected torque-proof with the shaft, such as an oil thrower, and extends into a reservoir for the lubricant being arranged beneath the shaft, for example in the bottom of the bearing housing. When the shaft turns, the oil ring turns with it transporting the lubricant into the bearing. Such oil rings are used both in rolling bearings and in journal bearings.
Especially in the field of pumping hydrocarbon fluids in the oil and gas industry the pumps are often exposed to very severe operating environments. For the offshore production of oil and gas, for example, it is nowadays common practice to use floating production storage and offloading units (FPSO) because the exploration moved to deeper waters and more distant locations. FPSOs are floating vessels used for the production and processing of hydrocarbons as well as for the storage of oil. A pump installed on such vessels has to operate in a maritime environment which causes—beside other difficulties—that during operation the entire pump is no longer stationary but undergoes quite strong movements. The bumpy sea moves the vessel and therewith the pump.
Thus, the pump suffers both a pitch and a roll motion. For a horizontal pump with horizontal bearings the pitch motion results in a deviation of the pump's shaft axis from the horizontal, i.e. the bearings of the shaft are moving up and down, whereas the roll motion results in a rotational movement of the entire pump around the shaft axis of the pump. Since the orientation of the pump relative to the vessel is usually not known before installation, in the following description the pitch and roll motion has to be understood in relation to the pump rather than in relation to the vessel or the FPSO, respectively.
Until now, the known design and technology of such pumps is generally sufficient for pitch and roll angles up to 5°, i.e. compared to the standard or desired orientation of a horizontal pump during operation the shaft axis may deviate from the horizontal up to 5° and the entire pump may be tilted or rotated up to 5° around the axis of the shaft of the pump. However, the requirements on pumps for maritime applications are increasing and there is a desire to safely operate pumps even for roll and pitch angles of more than 5°. It cannot be granted that the known technology will function for larger angles. Especially in bearings using an oil ring for the lubrication of the bearing element or journal a proper lubrication is no longer assured when the angle exceeds 5°. An insufficient or lacking lubrication is detrimental to the bearing and may result in a severe damage or even a failure of the bearing and therewith of the pump. Especially in offshore applications the complete breakdown of a pump bearing or a pump is a major incident that may result in large economic losses.